An average of more than one in 10 pupils were off school at any one time in two North Wales counties.

The worst was Denbighshire where 10.5% of half-day school sessions were missed, mainly due to sickness and other authorised absenteeism. But 1.9% was classed as unauthorised. Anglesey's figure stood at 10.3% absenteeism - with 1.4% unauthorised.

The assembly government set a target to reduce overall absenteeism in schools to below 8% by 2004.

Across Wales, absence rates fell slightly from 9.5% in 2002-3 to 9.4% last year, while unauthorised absence increased from 1.6% of sessions to 1.7%.

Education minister Jane Davidson announced yesterday £6m would be invested in electronic registration systems in Welsh schools to tackle truancy.

Ms Davidson said the latest figures were encouraging, showing a steady decrease from 10.6% in 1999.

Electronic registration had been shown to improve attendance, she said.

It provided instant information about individual pupils, allowing schools to react more quickly.

Denbighshire council said the high level of absenteeism and truancy in the county was closely linked to areas of deprivation such as Rhyl.

Measures taken to reduce absenteeism include increasing the number of educational social workers, truancy sweeps to search for young people who should be in school and contacting pupils' homes on the first day they fail to attend.

A council spokeswoman said: "The figures have increased because we now have better systems in place to track pupils who have authorised and unauthorised absences from school.

"Our main aim is to use youth, community and education services to engage young people and attract them back into mainstream education."

The national figures showed absenteeism varied in Wales from 11% of sessions in Cardiff to just 7.7% in Neath Port Talbot.

Unauthorised absence also varied from 3.3% in Cardiff to 0.5% in Merthyr Tydfil. Girls had a higher rate of overall absenteeism while boys were more often absent without permission.